Field of the Invention
The invention relates to a honeycomb body with passages through which a fluid can pass from one end to the other, in particular for a catalytic reactor for exhaust gases of an internal combustion engine of a motor vehicle, including structured, or smooth and structured, and in particular corrugated, sheet metal layers.
Honeycomb bodies of sheet metal layers of the specified kind are known, for example, from International Patent Application WO89/07 488. In that configuration smooth and corrugated sheet metal layers are disposed one upon the other alternately in a stack and twisted. Some of the sheet metal layers are thicker than others. The thicker sheet metal layers serve to increase the stability of the stack, in particular when it is fitted into a tubular casing. However, the provision of individual sheet metal layers of different thicknesses in the stack involves an increased level of manufacturing expenditure.
In certain uses of a honeycomb body, there is no need to provide individual thicker sheet metal layers for the purposes of increasing stability. In addition it is basically advantageous to make the sheet metal layers as thin as possible in order to reduce the weight and the costs of the honeycomb body. That aim, however, is in conflict with the aim of affording a high level of stability for the honeycomb body and long-term resistance to corrosion. Although most regions of a honeycomb body are only subjected to loadings which can be withstood even by very thin foils, there are nonetheless two difficulties in terms of using foils of a thickness of below 40.mu., in particular, for example, about 30.mu.. On one hand the production and in that respect in particular mechanical joining of the foils to each other and/or to a tubular casing is difficult when dealing with thin foils. Holes are very easily produced particularly when brazing or welding such thin foils. On the other hand, during operation, the ends of such honeycomb bodies are subjected to particular mechanical loadings due to pulsating flows and particular corrosion and erosion phenomena.
There are also situations of use for metal honeycomb bodies, for example in exhaust gas cleaning installations in motorized bicycles, in which heretofore relatively thick foils of a thickness of between 80 and 120.mu. were used, because of the high mechanical and/or corrosive loadings involved. In actual fact, as investigations have shown, in that situation the loading often occurs only in the end region.